title: Activation of human creatine kinase isoenzymes by pH and various sulfhydryl and chelating agents.
abstract: We report the effect of serum pH and of the presence or absence of mercaptoethanol, N-acetyl-L-cysteine, monothioglycerol, ethylenediaminetetraacetate, and ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetate on the activation of the human creatine kinase isoenzymes. At the serum pH giving maximal enzyme stability and minimal assay lag phase (Nealon et al., Clin. Chem. 26: 1165-1169, 1980) thiol activation of CK-1 and CK-3 is nearly maximal with monothioglycerol in an optimized creatine kinase assay (Szasz et al., Clin. Chem. 22: 650-656, 1976). However, CK-2 is maximally activated at pH 8.5, a pH at which this isoenzyme is least stable on storage and its assay lag phase is prolonged. These findings suggest irreconcilable problems in the storage, activation, and assay of CK-2.
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D002614:Chelating Agents / Q000494:pharmacology*; D003402:Creatine Kinase / Q000378:metabolism*; D004492:Edetic Acid / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D004789:Enzyme Activation; D005990:Glycerol / Q000031:analogs & derivatives / Q000494:pharmacology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007527:Isoenzymes / Q000378:metabolism*; D008623:Mercaptoethanol / Q000494:pharmacology; D013438:Sulfhydryl Compounds / Q000494:pharmacology*
chemical_list: D002614:Chelating Agents; D007527:Isoenzymes; D013438:Sulfhydryl Compounds; D004533:Egtazic Acid; D008623:Mercaptoethanol; D004492:Edetic Acid; C009465:thioglycerol; D003402:Creatine Kinase; D005990:Glycerol; D000111:Acetylcysteine